I expected that the Sauermann sounds somewhat "harder" or "brighter" then the simple symmetric but that was obviously not the case.

Does that mean the Sauermann sound "as good as or better than" the TSSA? I too expect a "harder" sound from balanced amp with the inexistence of second order harmonics. But Circlotron amps have good character too, probably because of speaker isolation from power supply ground.

Quote:

Originally Posted by Joachim Gerhard

On the other hand, a little third or ( and ) second does not seem to sound like distortion, rather more like "Character".

How about the "climbing" pattern of the distortion? I mean, it is not just 2nd order and 3rd but also 4th 5th 6th 7th 8th 9th and so on but with decreasing pattern towards higher end. Goldmund has this kind of distortion and they call it "natural" distortion (and I prefer that to other pattern resulting from adding beta enhancer to the VAS of the same topology)

Quote:

Originally Posted by Joachim Gerhard

The next candidate will be an Apogee
Duetta. If that works too it will be a surprise.

I think the TSSA has good drive ability (load has very little effect). At least in mine it is the most impressive that I have seen, along with its phase characteristics (don't know if that matters).

Goldmund and similar amps with high voltage rail for the double LTP have impressive THD at 20kHz, and it is audible in the performance of the trebles. But the TSSA has terrible THD at 20kHz. May be a balanced system will have much better THD at 20kHz? I'm trying to find out if simple class-A can have good THD at 20kHz. My 3-stage class-AB (similar to Fetzilla or P101) can have below 1%, far better than TSSA.

Goldmund and similar amps with high voltage rail for the double LTP have impressive THD at 20kHz, and it is audible in the performance of the trebles. But the TSSA has terrible THD at 20kHz. May be a balanced system will have much better THD at 20kHz? I'm trying to find out if simple class-A can have good THD at 20kHz. My 3-stage class-AB (similar to Fetzilla or P101) can have below 1%, far better than TSSA.

Hi Jay. This amp did already sound very good without a bufferstage before the mosfet. With the buffer the distortion is very very low even with a low idle current.

I played with your schematic and found while running Monte Carlo that a practical imbalance in the mirror currents can cause quite severe cross-over distortion. When I say practical, I mean real life components.

There certainly are several schools of thought concerning distortion. Some do not like distortion at all and it is possible to make power amps with complex compensation schemes and a lot of open loop gain that have even lower distortion then good preamplifiers. You can see examples on this forum.
Hiraga brought in another philosophy where the distortion should fall with order, even earlier the BBC made research on that and was suggesting a weighting scheme, higher order distortion being worse then lower order.
Latest research is from Geddes, again suggesting a metric, the Gedlee metric.
Especially Geddes allows quite a high amount of distortion before it gets an audible problem. In a private discussion Geddes told me that more or less all competent designed amplifiers with enough power to not show nasty behavior have low enough distortion to drive real world speakers.
So what is my personal experience
More later.
Just one little thing about the third harmonic. An analog tape recorder has a lot of third harmonic and usually does not sound sharp or bright. Maybe it is just plain wrong that a small dose of third sounds sharp.

To answer some more questions :
Do i think that the Sauermann is a good amplifier ?
Yes, i do and i also think it is a good value. He uses good parts and it is well build.
Do i think that my version of the Simple Symmetric is better ?
No, it is different but the differences are small, in the direction of taste. You could also say that the bass from the Sauermann is better controlled and tighter. I just was so mesmerized about the "massaging" effect that the Simple Symmetric had.
Never heard that before in such clarity.
You also have to consider that this assessment is only valid under the special circumstances. A speaker-room combination that is a bit overblown in the bass would certainly benefit from the Sauermann.
We where 3 experienced and professional listeners though and we heard very closely the same. That is quite rare so there is a good chance that it was real what we heard.

And the more detail and speed we heard from the Simple Symmetric ?
It may simply be that the Simple Symmetric has less damping factor so a peak in the impedance curve between tweeter and woofer may cause that effect by bringing out the presence range just a little. That also would explain the deeper soundstage of the Sauermann.
I do not have an impedance curve of the updated LQL200 so this is an estimation.
Maybe i can get the actual curve from the designer.
I think the amp-cable-speaker-room interface has to be considered as system or we are in muddy waters.